Self-tuning exhaust muffler

ABSTRACT

An exhaust muffler for a motor vehicle includes a louver tube having an intake end and an exhaust end. An outer tube, consisting of a frustoconical portion and a cylindrical portion, is concentrically arranged around the louver tube. A plurality of louvers and associated louver holes in the louver tube scoop a portion of gasses from the louver tube into the outer tube. An end cap, which includes an exhaust exit hole in its center, fits into an exhaust end of the outer tube. A plurality of end cap holes are arranged so that gasses leaving the outer tube flow through them. A restrictor disk between the end cap and louver tube includes a central hole coaxial with the louver tube and the exhaust exit hole of the end cap. Restrictor disk holes are in the restrictor disk between the central hole and its perimeter so that gasses leaving the louver tube flow through the central hole and the restrictor disk holes as they leave the muffler. A spiral vane defining a helical passage around the louver tube and inside the outer tube extends the path length of the gasses in the outer tube. A series of fins on the spiral vane extend orthogonal to an axis of the louver tube. A series of inner reverse cones are inside the louver tube upstream of its exhaust end. An exhaust system with this muffler is characterized by moderate backpressure at low rpms and little or negative backpressure at high rpms.

REFERENCE TO RELATED APPLICATIONS

[0001] This patent application is a continuation of copendingapplication Ser. No. 09/166,320, filed Oct. 5, 1998, entitled“SELF-TUNING EXHAUST MUFFLER”, which was a continuation of parent patentapplication Ser. No. 08/936,351, filed Sep. 24, 1997, now U.S. Pat. No.5,831,223. The aforementioned applications are hereby incorporatedherein by reference.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The invention pertains to the field of exhaust mufflers. Moreparticularly, the invention pertains to a self-tuning exhaust mufflerfor a motor vehicle, and especially a motorcycle, that reduces the soundwith minimal reduction in engine torque.

[0004] 2. Description of Related Art

[0005] A muffler is a device used to attenuate sound propagated inconjunction with a moving stream of fluid, usually a gas. Mufflersgenerally fall into two categories depending on how the sound energy isremoved from the gas stream: reactive and dissipative. A reactivemuffler, also known as a nondissipative muffler, attenuates the soundenergy by reflecting the sound back toward the source. A dissipativemuffler absorbs the sound energy as the gas passes through the muffler.Design considerations for the acoustical performance of a motor vehiclemuffler include: (1) the required sound attenuation as a function offrequency and length, (2) the effect on the exhaust gas flow andresulting system backpressures, and (3) the economics of manufacturingand installation.

[0006] The disadvantages of dissipative mufflers are numerous. Unburnedcarbon particles tend to close the pores of sound absorbing materialslining the walls of the muffler. The high velocity unsteady flow ofexhaust gasses blows out the fibers of the absorptive lining. Thermalcracking of the linings frequently occurs. There is poor attenuation atlow frequencies, i.e., on the order of the firing frequency, where mostof the exhaust noise is concentrated. Finally, there are relativelyhigher manufacturing costs as compared with a reactive muffler.

[0007] Most of the noise from a motor vehicle engine is at the firingfrequency and the first few harmonics. Exhaust noise from motor vehiclesgenerally consists of (1) sound generated when combustion gasses leavethe engine manifold and (2) sound generated when the exhaust gassesflows through the exhaust pipe. The first sound is in the form ofpulsating pressure waves that include frequency components proportionalto the engine speed. The first sound therefore has a relatively largeamount of low frequency components. The second sound has a relativelylarge amount of high frequency components. Low frequency noisecomponents are easily muffled with a modest size muffler. Motorcyclespresent a challenge to the noise engineer due to the limited mufflerspace available.

[0008] Motor vehicle mufflers are predominantly of the reactive type.Reflection is provided through acoustic filters, resonators, and changesin direction caused by bends in the pipe containing the gas stream.Reactive mufflers are useful in low frequency applications where thehigh temperatures or flammable exhaust gasses restrict the use ofdissipative materials. A primary characteristic of reactive mufflers isa relatively high pressure drop for a given value of gas flow velocity.This pressure drop exhibits itself as a back pressure at the exhaust ofthe engine, thereby restricting the engine performance. Back pressure isthe extra static pressure exerted by the muffler on the engine throughrestriction in the flow of exhaust gasses.

[0009] Conventionally, the muffler volume is proportional to the enginepiston displacement and inversely proportional to the engine speed andsquare root of the engine cylinders. This can be represented as:

[0010]${{Vol} = \frac{(K)({displacement})}{{rpm}\sqrt{{{no}.\quad {of}}\quad {cylinders}}}},$

[0011] where K values range from 5,000 for farm tractors, 1,000 foroff-highway trucks and heavy equipment, 35,000 for highway trucks, up to50,000 for passenger cars.

[0012] The fundamental frequency of piston-engine exhaust noise in theexhaust line is the product of the number of cylinders firing perrevolution and the engine speed, assuming the exhaust manifold has acenter outlet. If the exhaust manifold has an end outlet instead of acenter outlet, the frequency is reduced by half. For example, a 6cylinder 4-stroke cycle engine operating at 3,000 rpm has a fundamentalexhaust frequency of (6/2)(3,000/60)=150 Hz. The critical length of theexhaust pipe depends on the fundamental exhaust frequency and the meantemperature of the exhaust gasses. The critical length is λ/2 and allinteger multiples of λ/2 (harmonics), where λ is the wavelength of thesound in the exhaust pipe An exhaust muffler of the critical length setsup a standing wave with maximum pressure at the exhaust valves andminimum pressure at the end of the exhaust pipe. Assuming that theexhaust gas temperature in the exhaust pipe is such that the velocity ofsound is 1,500 fps, then the critical length of this engine is ½ of1,500/150=5 feet. Thus, 5 feet, 10 feet, etc. are critical lengths forexhaust lines in this engine.

[0013] The usual length to diameter ratio, l/d, is about 4:1, but can beas high as 8:1 in straight-through mufflers. A small l/d ratio mufflerattenuates the sound well for a narrow frequency band, whereas a largel/d ratio muffler attenuates the sound over a wider frequency band butnot as well.

[0014] Exhaust noise is appreciably reduced by filtering (frictioneffects) and using resonance chambers to offset the noise-wave effects.The total aeroacoustic attenuation in a moving medium (exhaust gasses)is a sum of the viscothermal effects and turbulent flow friction. Asimple expansion chamber 1 in a muffler 9 as shown in FIG. 1A iseffective for one relatively low noise frequency. Some friction is alsopresent due to a relatively small exit hole 2 in an exit plate 3. FIG.1B shows a baffle muffler 9 with control holes 4 in each baffle 5 thatintroduce friction effects. A plurality of chambers 6 are resonancechambers which have a very high frequency and are effective forfiltering a narrow band of high sound frequencies. FIG. 1C shows astraight-through muffler which has one resonating chamber 7 connected toa central perforated pipe with a plurality of perforation holes 8 but nobaffles or associated friction effects. FIGS. 1D and 1E showcombinations of baffles 5 and resonator chambers 7. FIG. 1F shows fourresonator chambers 7 of different frequencies which depend on the ratioof perforation area from perforation holes 8 to resonator volume. Thehigher this ratio, the higher the frequencies that are attenuated.

[0015] In general, torque is the ability of an engine to gain rpms,while horsepower is how much power the engine produces at a given rpm.Increasing backpressure increases torque in the low to mid-range rpms.After that, the torque decreases with increased backpressure. However,at mid-range rpms and higher, the horsepower decreases as thebackpressure increases. The mid-range rpms thus affect torque andhorsepower in different ways. In resistive muffler design, the generaltradeoff is that, as surfaces that reflect noise back toward the engineare increased (in order to reduce the noise), the overall back pressureexperienced by the system increases. Decreasing the back pressureusually increases the noise. Increased engine backpressure affects theengine timing and power output, as well as increasing unwanted exhaustpollutants.

SUMMARY OF THE INVENTION

[0016] Briefly stated, the present invention teaches an exhaust mufflerfor a motor vehicle includes a louver tube having an intake end and anexhaust end. An outer tube, consisting of a frustoconical portion and acylindrical portion, is concentrically arranged around the louver tube.A plurality of louvers and associated louver holes in the louver tubescoop a portion of gasses from the louver tube into the outer tube. Anend cap, which includes an exhaust exit hole in its center, fits into anexhaust end of the outer tube. A plurality of end cap holes are arrangedso that gasses leaving the outer tube flow through them. A restrictordisk between the end cap and louver tube includes a central hole coaxialwith the louver tube and the exhaust exit hole of the end cap.Restrictor disk holes are in the restrictor disk between the centralhole and its perimeter so that gasses leaving the louver tube flowthrough the central hole and the restrictor disk holes as they leave themuffler. A spiral vane defining a helical passage around the louver tubeand inside the outer tube extends the path length of the gasses in theouter tube. A series of fins on the spiral vane extend orthogonal to anaxis of the louver tube. A series of inner reverse cones are inside thelouver tube upstream of its exhaust end. An exhaust system with thismuffler is characterized by moderate backpressure at low rpms and littleor negative backpressure at high rpms.

[0017] According to an embodiment of the invention, an exhaust mufflerfor a motor vehicle includes a louver tube having an intake end and anexhaust end. An outer tube is concentrically arranged around the louvertube, with a frustoconical portion and a cylindrical portion. Thefrustoconical portion connects to the louver tube at the intake end. Aplurality of louvers and associated louver holes are in the louver tubewhereby a portion of gasses entering the louver tube are scooped intothe outer tube by the louvers through the louver holes. An end cap, withan exhaust exit hole in a center therein whereby gasses leaving theexhaust end of the louver tube flow through the exhaust exit hole, fitsinto an exhaust end of the outer tube. The end cap also has at least oneend cap hole therein whereby gasses leaving the outer tube flow throughthe end cap hole.

[0018] According to an embodiment of the invention, an exhaust mufflerfor a motor vehicle includes a louver tube having an intake end and anexhaust end. An outer tube is concentrically arranged around the louvertube, with a frustoconical portion and a cylindrical portion. Thefrustoconical portion connects to the louver tube at the intake end. Aplurality of louvers and associated louver holes are in the louver tubewhereby a portion of gasses entering the louver tube are scooped intothe outer tube by the louvers through the louver holes. An end cap, withan exhaust exit hole in a center therein whereby gasses leaving theexhaust end of the louver tube flow through the exhaust exit hole, fitsinto an exhaust end of the outer tube. The end cap also has at least oneend cap hole therein whereby gasses leaving the outer tube flow throughthe end cap hole. A restrictor disk is held against the exhaust end ofthe louver tube by the end cap. The restrictor disk has a central holetherein and at least one restrictor disk hole therein, whereby gassesleaving the exhaust end of the louver tube flow through the central holeand the restrictor disk hole before exiting the exhaust exit hole of theend cap. A spiral vane defines a helical passage around the louver tubeand inside the outer tube. At least one inner reverse cone is inside thelouver tube upstream of the exhaust end of the louver tube.

BRIEF DESCRIPTION OF THE DRAWING

[0019]FIG. 1A shows a block diagram of a prior art muffler with a simpleexpansion chamber.

[0020]FIG. 1B shows a block diagram of a prior art baffle muffler withcontrol holes centered in each baffle.

[0021]FIG. 1C shows a block diagram of a prior art straight-throughmuffler with a resonating chamber connected to a central perforatedpipe.

[0022]FIG. 1D shows a block diagram of a prior art muffler with acombination of baffles and resonator chambers.

[0023]FIG. 1E shows a block diagram of a prior art muffler with acombination of baffles and resonator chambers.

[0024]FIG. 1F shows a block diagram of a prior art muffler with fourresonator chambers.

[0025]FIG. 2 shows a partial sectional view of an embodiment of thepresent invention which includes a louver tube, an outer tube, and anend cap.

[0026]FIG. 3 shows a partial sectional view of an embodiment of thepresent invention which includes a louver tube, an outer tube, an endcap, and a restrictor disk.

[0027]FIG. 4 shows a partial sectional view of the end cap used in theembodiments of FIGS. 2 and 3.

[0028]FIG. 5A shows a top view of a restrictor disk with a central holeand a plurality of restrictor disk holes.

[0029]FIG. 5B shows a top view of a restrictor disk with a central holeand a plurality of restrictor disk holes.

[0030]FIG. 5C shows a top view of a restrictor disk with a central holeand a plurality of restrictor disk holes.

[0031]FIG. 5D shows a top view of a restrictor disk with a central holeand a plurality of restrictor disk holes.

[0032]FIG. 5E shows a top view of a restrictor disk with a central holeand a plurality of restrictor disk holes.

[0033]FIG. 5F shows a top view of a restrictor disk with a central holeand a plurality of restrictor disk holes.

[0034]FIG. 5G shows a top view of a restrictor disk with a central holeand a plurality of restrictor disk holes.

[0035]FIG. 6 shows an elevation view of a louver tube with a spiral vaneattached to it.

[0036]FIG. 7 shows a partial sectional view of the embodiment of FIG. 3used to explain the exhaust flow within the muffler.

[0037]FIG. 8 shows an embodiment of the present invention adapted to fitbetween an exhaust pipe and a tailpipe.

DETAILED DESCRIPTION OF THE INVENTION

[0038] Referring to FIG. 2, a muffler 10 of the present inventionincludes an inner tube such as a louver tube 20 and an outer tube 30.Louver tube 20 is preferably formed by punching a plurality of louvers22 inward into tube 20 so that a plurality of louver holes 23 permitfluid exchange between louver tube 20 and outer tube 30. Outer tube 30begins as a megaphone shape (frustoconical) and quickly assumes acylindrical shape. The angle between the frustoconical portion of outertube 30 and louver tube 20 can be varied to meet the desired performanceconditions (sound and backpressure) for the specific design application.The relative lengths of the frustoconical and cylindrical portions canalso be varied for the same purpose, as can be the diameter of outertube 30. Outer tube 30 can be double walled. Outer tube 30 preferablydoes not contain any dissipative material or other packing.

[0039] Exhaust gasses flow in a direction indicated by an arrow a intotube section 24 from an exhaust pipe (not shown) connected to an exhaustmanifold of an engine (not shown). The engine is either an internalcombustion engine or a diesel engine. The gasses entering muffler 10 canbe characterized as containing a high frequency sound producing portionand a lower frequency portion. The high frequency portion is generatedby friction effects while the low frequency portion is related to thefiring frequency of the engine. The high frequency portion in thisembodiment is caused by and generally concentrated near the outer wallsof the pipes or tubes comprising the total exhaust system. The highfrequency portion of the gasses entering louver tube 20 are thusdeflected by louvers 22 into outer tube 30. A tube chamber 25 acts as anexpansion chamber for the gasses entering muffler 10. The low frequencyportion remains in the center of louver tube 20 in a tube chamber 26.

[0040] As the low frequency portion flows through louver tube 20, highfrequency portions are created due to friction effects. These highfrequency portions continue to be siphoned off to outer tube 30 vialouvers 22. A plurality of inner reverse cones 40 near the far end oflouver tube 20 reflect additional high frequency components of thegasses back upstream while slightly constricting the flow of the lowfrequency portions through the end of louver tube 20, with a consequentslight increase in velocity of the low frequency portion. Inner reversecones 40 act partly as a choke and partly as a series of baffles. Thegasses in louver tube 20 leave muffler 10 through an exhaust exit hole32. In the embodiment shown for a motorcycle, an end cap 50 connected tothe ends of louver tube 20 and outer tube 30 includes a plurality of endcap holes 34 for the gasses in outer tube 30 to exit through.

[0041] Referring to FIG. 3, an embodiment of the present inventionfurther includes a restrictor disk 60 held in place by end cap 50.Restrictor disk 60 includes a plurality of disk holes 36 in addition toexhaust exit hole 32. A number, size, and shape of disk holes 36 can bevaried depending on the engine and other exhaust system parameters toachieve the desired effect (sound and backpressure effect). End capholes 34 can also be varied in a similar manner.

[0042] Referring to FIG. 4, end cap 50 includes an edge 55 that isoptimally sized to match an inner diameter of outer tube 30. End cap 50is preferably connected to outer tube 30 by several screws (not shown)extending through outer tube 30 into edge 55. Alternatively, edge 55 isthreaded and screws into corresponding threads (grooves) in outer tube30. The exposed outside diameter of end cap 50 at the upstream end isthus substantially the same as an outer diameter of outer tube 30. Asurface 51 is angled, preferably at approximately 30° from an axis ofmuffler 10, to provide a streamlining effect on the end of the muffler.A lip 56 on end cap 50 in conjunction with a concave edge 54 enhancesthe streamlining effect of end cap 50.

[0043] A length of lip 56 is preferably adjusted depending on the soundand backpressure effect desired for a particular engine and exhaustsystem. The length of lip 56 changes the diameter of the end of theexhaust system. The longer the length of lip 56, the more the liprestricts the flow and deflects the high frequency sound back into thelow frequency sound stream.

[0044] Concave edge 54 helps direct the outer flow coming both from theslipstream outside the muffler and from the gasses exiting outer tube 30back into the inner flow from louver tube 20. The angle concave edge 54makes with the muffler axis is optionally varied depending on thespecific application. Concave edge 54 helps create some back pressure atlow rpms and a negative backpressure at high rpms.

[0045] A leading edge 52 of end cap 50 is angled to improve the flowcharacteristic of the gasses in outer tube 30. Leading edge 52 acts as achoke to aid the airflow, and the angle also reflects some of the sound.An angle of leading edge 52 can be at right angles to the muffler axis,but such an angle increases turbulence and backpressure. An angle of 45°is preferable. An angled tip 53 of end cap 50 acts in similar fashion toleading edge 52.

[0046] Referring to FIGS. 5A-5G, a variety of restrictor disks 60 areshown. The size, shape, and location of restrictor disk holes 36 andexhaust exit hole 60 are optionally varied to achieve the preciseperformance and sound effect desired. FIG. 5A shows a series of circulardisk holes 36 arranged around exhaust exit hole 32. FIG. 5B shows twiceas many holes 36 as the embodiment of FIG. 5B. FIG. 5C shows eightelliptically shaped disk holes 36, while FIG. 5D shows sixteenelliptically shaped disk holes 36. FIG. 5E shows eight circular holes 36interspersed between eight elliptically shaped holes 36. FIG. 5F showssix slot-shaped holes 36. The size and shapes of the holes 36 shown hereare illustrative and not limiting. FIG. 5G shows an embodiment in whichthe holes 36 are threaded so that a person can easily vary the patternof holes simply by inserting or removing a threaded plug, such as a boltor screw 37, from the holes 36. The one common feature of the variousembodiments of the restrictor disks 60 is that every disk includes anexhaust exit hole 32. That is, the muffler 10 of this invention is not aplug-type muffler.

[0047] Referring to FIG. 6, an embodiment of the invention includes aspiral 70 attached to louver tube 20 and extending to the insidediameter of outer tube 30. Spiral 70 begins shortly after the firstlouver holes 23 and extends for at least several spirals along louvertube 20. Some of the exhaust gasses entering louver tube 20 at arrow aare scooped through louver holes 23, thus traveling around spiral 70inside outer tube 30 as shown by arrow b. An exact length of spiral 70depends on the specific application the present invention is designedfor. Spiral 70 ends before reaching end cap 50. Spiral 70 extends thephysical path length of the gasses inside outer tube 30. That is, thisembodiment makes use of a multiple length exhaust flow track. Spiral 70optionally includes a plurality of fins 72 along one or both spiralsurfaces which increase the conversion of low frequencies to highfrequencies in addition to reflecting the high frequency sound waves.Fins 72 are preferably angled towards the direction the gasses areflowing from, i.e., upstream.

[0048] Referring to FIG. 7, the flow of gasses in muffler 10 is shown.The low frequency portion flows substantially in the center of louvertube 10. High frequency portions stay near the outer wall of louver tube20 and are scooped into outer tube 30 by the louvers 22 through thelouver holes 23. The high frequency portions continue to the end ofmuffler 10 and exit through end cap holes 34. The ambient air from theslipstream is curved by surface 51 of end cap 50 and forces the highfrequency portions exiting end cap holes 34 into the high frequencyportions exiting louver tube 20 through restrictor disk holes 36. Inturn, both high frequency portions are forced into the low frequencyportion exiting louver tube 20 through exhaust exit hole 32. The resultis a mellow tone from which most of the high frequencies are removed.

[0049] Turbulence is created within the entire muffler at lower rpms.This turbulence decreases as the rpms increase. At low rpms, the centerflow at the exhaust end of muffler 10 does not provide any vacuum effect(Bernoulli effect) to the gasses flowing through end cap holes 34. Asthe rpms increase and internal turbulence decreases, the center flowthrough exhaust exit hole 32 smoothes out and causing a vacuum withrespect to the gasses flowing through end cap holes 34. The greater therpms, the greater the velocity of the exhaust gasses through exit hole32 and the greater the vacuum effect on the outer holes with aconsequent decrease in system backpressure. At high rpms, then, theexhaust system with muffler 10 is a high flow capacity system withoutstanding mid and top range engine torque and horsepower. At low rpms,the system with muffler 10 has a controlled backpressure for increasedtorque and fuel economy.

[0050] Referring to FIG. 8, an embodiment of muffler 10 is adapted as anin-line muffler in an exhaust system. End cap 50 is modified to connectto a tailpipe 65. The illustration shows only one variation of theconnection; other connections and angles between end cap 50 and tailpipe65 are considered to be within the capability of one skilled in the art.Restrictor disk 60 is still used. As stated with respect to aboveembodiments, the exact size, shape, and placement of disk holes 36 andend cap holes 34 depends on the performance characteristics required.

[0051] Accordingly, it is to be understood that the embodiments of theinvention herein described are merely illustrative of the application ofthe principles of the invention. Reference herein to details of theillustrated embodiments are not intended to limit the scope of theclaims, which themselves recite those features regarded as essential tothe invention.

What is claimed is:
 1. An exhaust muffler for a motor vehicle,comprising: a) a louver tube having an intake end and an exhaust end; b)an outer tube concentrically arranged around said louver tube, saidouter tube including a frustoconical portion and a cylindrical portion,said frustoconical portion connecting to said louver tube at said intakeend such that a smallest cross-sectional area of said frustoconicalportion is adjacent said intake end and a largest cross-sectional areaof said frustoconical portion is adjacent said cylindrical portion; c) aplurality of louvers and associated louver holes in said louver tubewhereby a portion of gasses entering said louver tube are scooped intosaid outer tube by said louvers through said louver holes; and d) an endcap fitting into an exhaust end of said outer tube; said end cap havingi) an exhaust exit hole in a center therein whereby gasses leaving saidexhaust end of said louver tube flow through said exhaust exit hole, andii) at least one end cap hole therein whereby gasses leaving said outertube flow through said at least one end cap hole wherein an exhaust flowfrom said vehicle is separated into first and second portions at anentry point of said muffler, and said first and second portions of saidexhaust flow are combined downstream in said muffler.
 2. An exhaustmuffler according to claim 1 , further comprising a restrictor disk heldagainst said exhaust end of said louver tube by said end cap, saidrestrictor disk having a central hole therein and at least onerestrictor disk hole therein, whereby gasses leaving said exhaust end ofsaid louver tube flow through said central hole and said at least onerestrictor disk hole before exiting said exhaust exit hole of said endcap.
 3. An exhaust muffler according to claim 1 , further comprising: aspiral vane defining a helical passage around said louver tube andinside said outer tube; and at least one fin on said spiral vaneextending orthogonal to an axis of said louver tube.
 4. An exhaustmuffler according to claim 3 , wherein: said spiral vane beginsdownstream of a first louver hole, said first louver hole being closestof all of said louver holes to said intake end of said louver tube; andsaid spiral vane ends downstream of a last louver hole, said last louverhole being closest of all of said louver holes to said exhaust end ofsaid louver tube.
 5. An exhaust muffler according to claim 1 , furthercomprising at least one inner reverse cone inside said louver tubeupstream of said exhaust end of said louver tube.
 6. An exhaust muffleraccording to claim 1 , further comprising: at least two end cap holes;and at least one of said two end cap holes being threaded to receive athreaded plug.
 7. An exhaust muffler according to claim 1 , wherein saidmotor vehicle is an automobile powered by one of an internal combustionengine or a turbo-charged diesel engine.
 8. An exhaust muffler accordingto claim 1 , wherein said motor vehicle is a motorcycle.
 9. An exhaustmuffler according to claim 1 , wherein said motor vehicle is a truckpowered by one of an internal combustion engine or a diesel engine. 10.An exhaust muffler according to claim 1 , wherein said motor vehicle isa piece of heavy equipment powered by a diesel engine.
 11. An exhaustmuffler according to claim 1 , wherein said louver tube is shaped as acylinder and said cylindrical portion of said outer tube is congruent tosaid louver tube.
 12. An exhaust muffler for a motor vehicle,comprising: a) a louver tube having an intake end and an exhaust end; b)an outer tube concentrically arranged around said louver tube, saidouter tube including a frustoconical portion and a cylindrical portion,said frustoconical portion connecting to said louver tube at said intakeend; c) a plurality of louvers and associated louver holes in saidlouver tube whereby a portion of gasses entering said louver tube arescooped into said outer tube by said louvers through said louver holes;d) an end cap fitting into an exhaust end of said outer tube, said endcap having i) an exhaust exit hole in a center therein whereby gassesleaving said exhaust end of said louver tube flow through said exhaustexit hole, and ii) at least one end cap hole therein whereby gassesleaving said outer tube flow through said at least one end cap hole; e)a restrictor disk held against said exhaust end of said louver tube bysaid end cap, said restrictor disk having a central hole therein and atleast one restrictor disk hole therein, whereby gasses leaving saidexhaust end of said louver tube flow through said central hole and saidat least one restrictor disk hole before exiting said exhaust exit holeof said end cap; f) a spiral vane defining a helical passage around saidlouver tube and inside said outer tube; and g) at least one innerreverse cone inside said louver tube upstream of said exhaust end ofsaid louver tube.
 13. An exhaust muffler according to claim 1 , furthercomprising: (e) a spiral vane defining a helical passage around saidlouver tube and inside said outer tube.
 14. An exhaust muffler accordingto claim 1 , further comprising: (e) at least one inner reverse coneinside said louver tube upstream of said exhaust end of said louvertube.
 15. An exhaust muffler for a motor vehicle, comprising: a) alouver tube having an intake end and an exhaust end; b) an outer tubeconcentrically arranged around said louver tube, said outer tubeincluding a frustoconical portion and a cylindrical portion, saidfrustoconical portion connecting to said louver tube at said intake endsuch that a smallest cross-sectional area of said frustoconical portionis adjacent said intake end and a largest cross-sectional area of saidfrustoconical portion is adjacent said cylindrical portion; c) aplurality of louvers and associated louver holes in said louver tubewhereby a portion of gasses entering said louver tube are scooped intosaid outer tube by said louvers through said louver holes; and d) an endcap fitting into an exhaust end of said outer tube; said end cap havingat least one end cap hole therein whereby gasses leaving said outer tubeflow through said at least one end cap hole wherein an exhaust flow fromsaid vehicle is separated into first and second portions at an entrypoint of said muffler, and said first and second portions of saidexhaust flow are combined downstream in said muffler.
 16. An exhaustmuffler according to claim 15 , wherein said end cap includes an exhaustexit hole in a center therein whereby gasses leaving said exhaust end ofsaid louver tube flow through said exhaust exit hole.
 17. An exhaustmuffler according to claim 15 , further comprising: (e) a restrictordisk held against said exhaust end of said louver tube by said end cap,said restrictor disk having at least one hole therein.
 18. An exhaustmuffler according to claim 17 , further comprising: (f) at least oneinner reverse cone inside said louver tube upstream of said exhaust endof said louver tube.
 19. An exhaust muffler according to claim 15 ,further comprising: (e) at least one inner reverse cone inside saidlouver tube upstream of said exhaust end of said louver tube.
 20. Anexhaust muffler for a motor vehicle, comprising: means for separating anexhaust flow from said vehicle into first and second portions at anentry point of said muffler; means for combining said first and secondportions of said exhaust flow downstream in said muffler; wherein afirst path length of said first portion of said exhaust flow is longerthan a second path length of said second portion of said exhaust flow.21. A muffler according to claim 20 , wherein said first and secondportions of said exhaust stream are combined at an exhaust exit point ofsaid muffler.